1. Field of Invention
The present invention relates to a wing/flap assembly and method for an aircraft, and more particularly to such an assembly which is designed to reduce adverse effects of wake producing devices, such as landing gear or flap track faring.
2. Background Art
Aircraft wings are commonly provided with trailing edge flaps which are positioned in a stowed position in the aft portion of the main wing for cruise, and for landing are deployed to their high lift position where the flaps form a slot with the rear portion of the wing. However, it commonly happens that the performance of the wing and trailing edge flap combination are adversely affected when a wake producing device, such as a landing gear or a flap track faring is located forwardly of the slot formed by the flap and the wing so as to produce turbulent wake flow that flows through the slot and over the upper surface of the wing.
Various solutions to this problem have been tried. One is to add a slot or slots in the flap itself so that air from beneath the flap flows upwardly through the slot formed in the flap to then flow over the upper flap surface, and thus delays the onset of separated flow. However, these added slots increase the cruise airfoil drag and have additional cost associated with the slot addition. Another technique is to add vortex generators on the flap leading edge to reduce separation in the extended position. However, it has been found that such vortex generators have minimal effect on a highly loaded flap. Yet another approach has been simply to streamline the wake producing object. While this can produce some benefit, this requires additional faring to streamline the upstream object that causes the disturbance.
A search of the patent literature has disclosed a number of patents, these being the following.
U.S. Pat. No. 4,131,252 (Dean et al) shows a wing and trailing edge flap configuration arranged to compensate for airflow blockage at the slotted area of the flap. There is a recessed area in the upper surface of the flap in the area of the blockage, and there is a slot leading from the lower surface of the flap upwardly into the rear area of the recess to provide additional air flow to compensate for the air flow blockage.
U.S. Pat. No. 3,199,813 (Roper) illustrates an airfoil pod mounted to an edge of the wing having an inner side surface aerodynamically contoured to match the direction of flow over the upper and lower surfaces of the wing.
U.S. Pat. No. 3,756,540 (Williams) shows an airfoil where there is along the chord length five sections producing specialized flow patterns over each section. At the aft end of the airfoil there is a concave region, and a tangential slot is placed at the trailing edge to produce flow over and around a Coanda profile to prevent flow separation.
U.S. Pat. No. 3,478,988 (Roed) discloses a STOL aircraft having by-pass turbojet engines where trailing edge flaps are positioned to provide various flow conditions for Stol operation and also for aerodynamic braking.
U.S. Pat. No. 4,426,054 (Wang) discloses an upper surface blown powered lift system where the jet exhaust is discharged over the upper surface of the wing, and it is deflected downwardly by the Coanda effect over the upper surface of downwardly deflected flaps for Stol aircraft operation.
German Patent No. 665,964 (a translation not being presently available) shows a trailing edge device which apparently can be deflected from an aerodynamically contoured cruise configuration to a position where the rear end of the device slants upwardly and rearwardly.